A bit after the fact, but still very interesting information. How Openstreetmap has been used to help NGO’s work in Haiti after the earthquake. A specific webpage has been set up for the occasion: http://www.openstreetmap.org.ph/

«A simple trick illustrates topology: taking off a vest without taking off a coat, since (topological) the vest is outside the coat — in the sense that a paper lying on the bottom of a wastebasket is really outside the basket, not in it, since being in would require removal of a boundary. One puts an arm through one vesthole; pulls the coat through this vesthole until it is hanging on the other arm; then pulls the through that other vesthole, where it is obviously "outside".»